Production of light metals, such as magnesium



March 7, 1933: v E. Q -row 1,900,220

PRODUCTION OF LIGHT METALS, .SUCH AS uAGNEsiUu Filed Dec-. 20, 1929 I INVENTOR BY @a/wlmr ORNEY Patented Mar. 7, 1933 UNITED STATES PATENT OFFICE EDWIN O. BARSTOW, OF MIDLAND, MICHIGAN, ASSIGNOIR- TO THE DOW CHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN PRODUCTION OF LIGHT METALS, SUCH AS MAGNESIUM Application filed December 20, 1929. Serial No. 415,456.

In the electrolytic production of light metals, such as metallic magnesium by electrolysis of a suitable fused electrolyte to the surface of which the liberated metal rises as separate molten globules and upon which electrolyte such metal floats, there is presented the problem of collecting such metals separately from the other products of electrolysis, agglomerating or consolidating the separate globules thereof into a consistent mass and the removal of the metal so produced from the electrolytic cell.

The object of the present invention is to provide an improved method and apparatus whereby such free molten globules of the metal may be promptly drawn together within a predetermined limited area of the bath surface, and from that area or point of collection be transferred into a defined well or other suitable vessel, such drawing together and transferring being done by mechanical means.

The invention may be regarded as an improvement upon the method and means dis closed and claimed in my copending application, Serial No. 67,780, filed November 9, 1925, entitled Production of light metals, since issued as Patent No. 1,755,380 under date April 22, 1930.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps and means hereinafter described and particularly pointed out in the claims, the annexed drawing and following description illustrating but several of the various ways in which the principle of the invention may be carried out.

In said annexed drawing Fig. 1 is a plan view of one type of electrolytic cell which I have found adapted to the production of magnesium metal by the electrolysis of a fused bath containing magnesium chloride. Fig. 2 is a vertical cross-section of said cell on the line wb in Fig. 1. Fig. 3 is a part vertical cross-section upon the line a 0-d of Fig. 1. For the sake of clarity, the

above figures are more or less diagrammatic and incomplete with reference to such details as concern only the electrolysis of fused baths. prominence being given to such features of construction as are concerned with the collection of the floating metal as disclosed here- 1n.

' Referring now to the drawing, the vessel 1 is the cathode pot adapted to contain a suitable fused bath. Such vessel may be set in a furnace or otherwise properly related to an outside source of heat. A central anode 2 dips in the bath and is surrounded by a curtain 3, having a cover 4, forming an inverted bell dipping in the bath in which the gaseous anode products may be trapped and from which they may be led away as desired, as via the outlet 5 in the cover 4 thereof. The electric current connections will be made to the pot and to the anode in such manner that the pot will act as the cathode and metal will be liberated thereon and rise by reason of its lower gravity through the bath to the surface thereof as indicated at 6. Such metal tends to float upon the bath in more or less distinct globules or isolated masses, presenting a large surface exposure to oxidation or other deleterious attack, and it becomes advisable to remove the metal as promptly as possible to a more secure or safe location in order to conserve it.

In the said copending application I have disclosed a method of collecting the dispersed globules of floating metal in a definite surface area of the bath by causing the bath to circulate through a trap in which the floating metal is arrested and in which it may accumulate. Experience with this method suggested the advantage which would be secured provided the metal could be collected to a very substantial depth in a defined collecting zone in which it could safely remain while consolidating and permitting entrained electrolyte, oxide and other impurities to separate, whereby the metal would be refined before removal from the cell. If the metal be mere- 1y assembled into one spot or limited area by circulation of the bath. but a shallow layer may be collected because of the hydrostatic head developed by such accumulating metal, since with a considerable depth of metal the upper surface thereof will be at a level, elevated substantially above the bath and the lower surface will also be at a level depressed substantially below such surface. The collection of the metal in a thin layer necessitates frequent removal, whereas if collected in a deep layer, removal at infrequent intervals could be practiced and not only would the mechanics of purification and separation be bettered, but a larger output per unit of labor and heat loss incident to such removal operations would result. Accordingly. I have conceived the method of and means for mechanically transferring the metal from the surface of the electrolyte into a defined collecting well wherein it may accumulate to a substantial depth of even a foot or more, if desired, in contact with the bath at its lower surface. The metal may be dipped, or lifted. or pumped. or transferred, by any preferred method'or by any preferred means, with or without circulation of the bath, as disclosed in my copending application and with or without entrapping the metal carried by said circulating bath. However. a simple preferred method involves the circulation of the bath, causing the metal floating thereon to pass the location of the dipping or metal elevating and transferring device. at which point a trap or dam or bar may be installed in the bath to arrest the metal in position for the lifting device to pick it up for transfer to the collecting well.

The collecting well may be formed integral with the pot by partition walls rising above the level of the bath and extending as well to a sufficient depth therein, or it may be comprised of a separate member hung or supported in the bath, or again it may be an entirely separate Vessel outside of the electrolytic cell proper.

I have illustrated in the drawing. however, a collecting well formed by suspending or otherwise supporting in the bath a separate member adapted to partition ofl' therein a zone suitable to serve as the collecting well. Referring again to the drawing. 7 is the collecting well. defined by the curved segmental Wall 8. along the pot wall and the chordal wall 9, by means of which a definite portion of the pot is enclosed. The walls 8 and 9 are extended sufficiently above the bath as well as sufliciently below same to permit the accumulation therein of metal to a substantial depth. as indicated in Fig. 3. ln order to deliver the floating metal into the collecting well, I provide preferably a dipper 10, carried upon a hollow shaft 11, and caused to rotate as indicated by the arrow by means of a chain drive 16 from the pulley driven shaft 15. The dipper 10 is comprised of a hollow box with an aperture upon one side, so constructed that when rotated it will dip, at each rotation, a suitable quantity of the metal floating upon the surface of the bath, picking same up with or without electrolyte, and deliver the so picked up metal and/or electrolyte through the hollow shaft thereof into the well 7. 12 is a paddle-wheel carried upon the shaft 15,

the blades of which dip in the bath and upon revolution cause the bath to circulate in the direction of the arrows by means of which the floating metal 6 is brought to the dipper 10. A bar 13 dipping in the bath is so placed as to trap and arrest the metal at the dipper, thereby enabling the so arrested metal to be picked up by the dipper in due course. A partition 14 may be advisedly employed, having an apron in juxtaposition to the paddlewheel 12, whereby the effectiveness of the paddle-wheel in causing circulation of the ath is improved.

The paddle-wheel, dipper, and well may be constructed in one unit, if desired, such unit being removable from the cell and replaceable therein at will. The operations of circulating and dipping may be both continuous or both intermittent, or the drives for the dipper and paddle-wheel may be separate and either may be operated continuously or intermittently as preferred. If the collecting well be a separate outside vessel, it may, if desired, contain a fused bath of suitable character and be provided with a method of heating to maintain fluidity while the collected metal is contained therein, and means may be further provided to return from such separate collecting vessel or well excess bath removed from the cell to it with the metal. The precise construction of the circulating means for the bath may also vary through a wide range without departing from the spirit of my invention, such details adapting themselves to the various types of electrolytic cells employed, whether containing one or a plurality of anodes, or whether having a circular, rectangular, or other form and the like, and similarly, various structures and mechanisms may be employed to dip or transfer the metal to the collecting well without departing from the spirit of my invention. I wish it to be further understood that a curtain or diaphragm is not an essential element in the electrolytic cell when applying my invention. Under certain conditions, such an element may be entirely dispensed with and advantages realized thereby if my invention herein disclosed is employed.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and dis tinctly claim as my invention 1. In a method of electrolyzing a fused electrolyte for the production of a metal which will float thereon, the step which consists in elevating and transferring the floating metal so produced to a defined collecting well in the electrolyzer, wherein the so transferred metal may be retained and accumulate to a substantial depth while in contact with said electrolyte at the lower surface of the mass of metal so retained.

2. In a method of electrolyzin a fused electrolyte for the production 0 a metal which will float thereon, the steps which consist in mechanically circulating at least the surface portion of said electrolyte through a zone adapted to hold back metal floating thereon and the elevating and transferring the said metal to a collecting reservoir in the electrolyzer.

3.,In a method of electrolyzing a fused electrolyte for the production of a metal which will float thereon, the steps which consist in mechanically circulating at least the surface portion of said electrolyte through a zone adapted to hold back metal floating thereon and then elevating and transferring the said metal to a defined collecting reservoir in the electrolyzer, wherein the so transferred metal may be retained and, ac-

cumulate to a substantial depth.

4. In a method of electrolyzing a fused electrolyte for the production of a metal which will float thereon, the steps which consist in mechanically circulating at least the surface portion of said electrolyte through a zone adapted to hold back metal floating thereon and then elevating and transferring the'said metal to a defined collecting reservoir in the electrolyzer, wherein the so transferred metal may be retained and accumulate to a substantial depth while in contact with the electrolyte at the lower surface of the mass of metal so retained.

5. The method of aggregating light metal floating on a fused electrolyte, which comprises mechanically circulating said electrolyte through a zone in which the floating metal is arrested and then elevating and transferring the so restrained metal to a defined collecting well adapted to permit retention of such metal to a substantial depth while in contact with electrolyte at the lower surface of the mass of metal so retained.

6. In an electrolytic apparatus for producing a fused metal lighter than the fused electrolyte employed, the combination with a suitable vessel adapted to contain said fused electrolyte of a defined well adapted to contain a mass of fused metal of substantial depth floatingupon fused electrolyte therein, and mechanically driven means to elevate and transfer metal floating upon said electrolyte in said vessel to said well.

7. In an electrolytic apparatus for producing a fused metal lighter than the fused electrolyte employed, the combination with a suitable vessel adapted to contain said fused electrolyte, of a trap disposed within said vessel in said electrolyte to arrest and retain floating metal, a mechanically driven means in said vessel to circulate the electrolyte upon which the metal floats through said trap, a

defined collecting well adapted to contain a mass of metal of substantial depth and a mechanically driven means to transfer the arrested floating metal to the collecting well.

8. In an electrolytic apparatus for producing fused metal lighter than the fused electrolyte employed, the combination with a suitable vessel adapted to contain said fused electrolyte, of a mechanically driven paddlewheel dipping in said electrolyte and adapted to cause same to circulate in said vessel, :1 defined collecting well for metal, and a mechanically driven dipper adapted to take up metal floating on the circulated electrolyte and transfer it to said collecting well.

Signed by me this 16th day of December, 

